Zinc vs. Aluminum Anodes

Mil-Spec zinc and Mil-Spec aluminum anodes provide excellent corrosion protection
for steel and aluminum hull vessels that operate in salt or brackish water. Both are
very effective. Historically, zinc anodes have been less expensive than aluminum but that's no longer the case. The more active, longer lasting aluminum anodes are now less expensive, making them a clear favorite for most commercial applications.

The difference between zinc and aluminum anodes is summarized below:

Zinc
MIL-A-18001K

Aluminum
Mil-A-24779(SH)

Voltage (1)

-1050 mV

-1100 mV

Density

0.258 lbs per cubic-inch

0.105 lbs per cubic-inch

Energy Capacity

368 amp-hours per lb

1150 amp-hours per lb

Service Life (relative to Zinc)

100%

120%

Cost (relative to Zinc)

100%

80%

(1) Galvanic voltage produced relative to a silver/silver-chloride electrode in seawater.